I try to match the fabric I am sewing. When I quilt sometimes I like to have a contrasting thread - on some quilts I like that to show especially if I have a pretty color of thread.
I have never used Aurifil thread.. but I am going to check it out right now.
I recently starting using King Tut brand from Fabric.com... has anyone used that? I love the colors but it seems pricey (but I still spent the money on it anyway)